Three years after giving us the third highest-grossing film of all time, Marvel's superhero dream team reassembles in Avengers: Age of Ultron. If you've already forgotten what happened in that 2012 blockbuster,

which has been followed by sequels to three Avengers' individual film series, there is no need to brush up on the alien invasion on New York City. What's done is done and this squad of six has new fish to fry, none of which have much to do with anything previously teased or explored in the so-called Marvel Cinematic Universe.

The follow-up opens with Iron Man (Robert Downey Jr.), Captain America (Chris Evans), Thor (Chris Hemsworth), Hulk (Mark Ruffalo), Black Widow (Scarlet Johansson), and Hawkeye (Jeremy Renner) back in action, working together. The specifics of the opening set piece are of minimal importance. All you must know is that it would take an extraordinary force to challenge the technology, weapons, and powers of this fierce, sexy sextet.

Though they reclaim a potent scepter wielded by Loki (who is sadly a no-show this time around), the gang is tested by the Maximoffs, Eastern European twins who have been enhanced by genetic experiments. He (Aaron Taylor-Johnson) displays super speed, while she (Elizabeth Olsen) can infiltrate and manipulate minds. The orphaned siblings are formidable foes, but they are not the film's main antagonists. That duty is filled by Ultron, an artificial intelligence program that Iron Man and Hulk's alter egos have been developing in secret, unbeknownst to even their fellow Avengers.

Ultron, designed to bring peace to the world, occupies a robotic body and soon exhibits a mind of his own. He wreaks havoc on Iron Man's trusted virtual manservant J.A.R.V.I.S. and then plots to achieve world peace by mass destruction.

Per Marvel's winning formula, Age of Ultron offers plenty of comedy and plenty of action. As you'd expect, the former element is in abundance during the film's first half, while the latter dominates later acts.

Adding to a tradition that can be traced back to the original Spider-Man in 2002, a Marvel production will launch Hollywood's summer movie season. This sequel is basically guaranteed to be the biggest hit yet from the wildly successful, Disney-owned comic book factory's studio. One assumed that a movie bringing together iconic personalities plenty popular on their own would generate even more excitement and ticket sales. Still, the $623 million domestic and $1.5 billion worldwide grossed by the first Avengers exceeded every expectation and every superhero movie to come before.

Disney/Marvel has ingenuously turned a number of lucrative franchises into one giant mega-franchise whose grip on entertainment dollars isn't likely to loosen anytime soon. Sure, the present superhero movie boom will someday slow and eventually end. Until then, Marvel is Hollywood's king and their kingdom consists of multiple layers of interconnected event tentpoles. While the post-Avengers sequels of Iron Man, Thor, and Captain America all defied the norm and exceeded their predecessors commercially, this first proper Avengers sequel takes "must-see" to new heights. This is far from the end, too, with Captain America and Thor threequels due in 2016 and 2017 in addition to a spate of origin films (July's Ant-Man, 2016's Doctor Strange, 2018's Black Panther). The first weekends in May 2018 and 2019 have already been claimed by the two-part finale of the Avengers saga, tentatively subtitled Infinity War. There is also more Guardians of the Galaxy and then there is chief competitor DC Comics' full upcoming slate of ten scheduled movies through 2020, starting with the much-anticipated Batman v. Superman: Dawn of Justice next year.

In light of all this, it seems very likely that fatigue will bring about the end of this superhero movie age. The fatigue of audiences and of the actors, writers, and directors entrusted with adapting these comic book universes for the big screen in all the splendor that big budget cinema currently allows.

Even if, like me, you regard Marvel's endeavors as some of the finest films being made today, you might find yourself getting a little too familiar with the forms and formulas of the studio's efforts. Last year's top-grossing Marvel movie, Guardians of the Galaxy, exceeded the first Avengers for me by unearthing new levels of charm with unconventional, heretofore unknown characters. By comparison, the Avengers aren't as dynamic, even with the sleek costumes, witty banter, and muscular physiques with which they are equipped. Over the last seven years, we've spent between four and five movies with most of these leads and even those that perfectly marry actor and persona, like Downey as de facto leader Tony Stark, appear to be on the verge of tedium.

Fortunately, writer-director Joss Whedon, this time flying entirely solo, brings the material certain instincts he sharpened on years of creating and showrunning television shows. Whether those shows endured ("Buffy the Vampire Slayer") or not ("Firefly"), they all inspired passionate cult followings, who were motivated to keep coming back. Whedon packs at least half a season's storylines into the ample 2½-hour runtime. Two Avengers strike up a romance, despite some misgivings. One Avenger reveals they've had a secret family for years, who they can turn to for shelter when no else can be trusted. Almost all of the gang wrestles with some demons in the form of lingering fears from their past.

On a fundamental level, Age of Ultron is more of the same. Even if its end promises sweeping change in the form of wildly revised line-up, everything up until then is again dividing screentime among these established heroes who accept the role of being the planet's first line of defense. There are cameos made by past supporting players, Stan Lee, and characters of future significance, the last of which comes early into the end credits (so no need to wait until the scroll ends). Those who don't appear (like Gwyneth Paltrow and Natalie Portman's characters) do get mentioned by name.

You don't need to be a clairvoyant to foresee Age of Ultron becoming well-reviewed (if less so than its predecessor) and the biggest global blockbuster of 2015. It'd be a much bigger surprise if Marvel genuinely disappointed the public and even then the studio would be more likely to do so on something riskier and less lucrative. Illustrating how important the rest of the world has become to Hollywood's bottom lines, Age of Ultron opened in a number of Eastern Hemisphere territories last week, including Russia, France, Australia, and South Korea (one of a few foreign locations prominently and tactfully featured in the film). The film has already grossed over $200 million from the 17 early debuts and that is clearly just the start of what is destined to be another billion dollar haul.